In my left shoulder area, a heaviness starts, goes down the arm, within a half hour, it's down to the knee, lasts for a little bit, then the heaviness turns into a dull pain, with my left hand going numb. Then it lasts for about an hour longer, then it all goes away. And it happens about every three or four days, for the last month. Do you have any idea why this is happening, or what it means?